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ULTRA HIGH RESOLUTION MAGNETICS FOR ARCHEOLOGICAL INVESTIGATIONS
Jim Bruseth of the Texas Historical Commission recently presented a paper in Mobile Alabama entitled "Recent Excavations at Texas' Presidio Nuestra Señora del Loreto y la Bahía". The talk reviewed excavation work done at the La Salle fort (ca. 1730) in southern Texas over the last 2 years. Rob Huggins and Lynn Edwards of Geometrics conducted the first magnetometer survey, using a non-magnetic cart of our design. Two G-858 gradiometers in a transverse configuration for a wide swath were employed. The astonishing results are displayed below showing a 200 m x 200 m area surveyed at 0.5m intervals. The presidio is clearly identified by the area of low magnetic relief in the center and the area outside the fort wall is detected as a refuse area where many small targets can be seen. The survey took approximately 3 days and Jim tells us that over the last 2 years they have been excavating sections of the site based on those magnetic findings, where literally every small magnetic anomaly has been determined to be an artifact of one sort of another.
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